Method and compositions for preventing or reducing aluminosilicate scale in alkaline industrial processes

ABSTRACT

Materials and a method are provided whereby polymers with least 0.5 mole % of the pendant group or end group containing —Si(OR″) 3  (where R″ is H, an alkyl group, Na, K, or NH 4 ) are used to control aluminosilicate scaling in an industrial process having an alkaline process stream such as a pulping mill process stream. When materials of the present invention are added to the alkaline process stream, they reduce and even completely prevent formation of aluminosilicate scale on equipment surfaces such as evaporator walls and heating surfaces. The present materials are effective at treatment concentrations that make them economically practical.

This application which is a continuation in part of Ser. No. 10/780,302filed on Feb. 17, 2004, which is in turn a divisional of Ser. No10/201,209 filed on Jul. 22, 2002, now U.S. Pat. No. 6,814,873, claimsthe benefit under 37 CFR §120 of U.S. Provisional Application No.60/651,347 filed on Feb. 09, 2005.

SUMMARY OF THE INVENTION

The invention describes materials and methods for preventing orinhibiting the formation of scale on or in equipment used in industrialprocesses having alkaline process streams.

BACKGROUND OF THE INVENTION

The problem of scaling in and on process equipment used in industrialprocesses and particularly in those having an alkaline process stream isvery well known. The scales present a significant problem when theybuild up on the surface of process equipment and cause a loss in theheat transfer coefficient. Thus, additional heat may be required to beprovided to the evaporator equipment in these processes resulting inadded cost.

An example of such an industrial process having an alkaline processstream is the Kraft recovery process for manufacturing paper which hasbeen known for over 100 years and is eloquently described in many textson the subject (see G. A. Smook “Handbook for Pulp and papertechnologists, 3rd Edition). More recently the development of closedloop cycles in kraft paper mills has resulted in an increase in scalingproblems in process equipment due to the build up of aluminum andsilicon in the system as is described by P. N. Wannamaker and W. J.Frederick in “Application of solubility data to predicting theaccumulation of aluminum and silicon in alkaline pulp mills”, MinimumEffluent Mills Symposium, 1996, p303. This article describes theoccurrence of aluminosilicate scales in the black, green and whiteprocess liquors streams of the Kraft process. When the scales form onthe surface of black liquor evaporators, tough glassy scales which aredifficult and costly to remove, are formed. It has, therefore, been awell recognized need to provide a method for inhibiting the formation ofaluminosilicate scales in kraft pulp mills. U.S. Pat. No. 5,409,571describes the use of terpolymers of maleic acid, acrylic acid andhypophosphorous acid as scale inhibitor for kraft pulp mills. This typeof polymer is shown to be effective against calcium carbonate scales buthas not been shown to be effective for aluminosilicate scales.

SUMMARY OF THE INVENTION

The present invention solves the aforementioned problems and others byproviding materials and a method whereby polymers having at least 0.5mole % of the group —Si(OR″)₃ (where R″ is H, an alkyl group, Na, K, orNH₄) as an end group or pendant thereto are used to reduce or eliminatealuminosilicate scaling in a process having an alkaline process streamsuch as a kraft pulping mill. When materials of the present inventionare added to kraft pulp mill process streams, they reduce and evencompletely prevent formation of aluminosilicate scale on the equipmentsurfaces. Moreover, the present materials are effective at treatmentconcentrations that make them economically practical.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a method and materials for thereduction of aluminosilicate containing scale in an industrial processhaving an alkaline process stream such as in the kraft pulp mill processstreams. The process stream to be treated can be any process streamhaving an alkaline condition and in which scaling occurs, e.g. black,green and white liquors of the kraft process.

The method comprises the step of adding to the process stream analuminosilicate containing scale inhibiting amount of a polymer havingat least 5 mole % pendant thereto a group or end group containing—Si(OR″)₃ where R″═H, C1-C3 alkyl, aryl, Na, K or NH₄. The amount of—Si(OR″)₃ functionality present in the polymer will be an amountsufficient enough to achieve the desired results and can range from alittle as 0.5 mole % of the total monomer groups present in the polymerto as much as 100 mole %. However it will be most economical to use theleast amount necessary to yield the desired results. The polymers arepreferably prepared initially as the silylether derivatives Polymer—Si(OR″)₃ where R″═C1-C3 alkyl, aryl, eg Polymer —Si(OCH₂CH₃)₃ orPolymer—Si(OCH₃)₃. The silylether derivatives may be added directly tothe industrial process stream such as a kraft pulping mill processstream or they may be hydrolyzed to the silanol derivatives to formpolymers of the following generic structures, Polymer—Si(OH)₃,Polymer—Si(ONa)₃, Polymer—Si(OK)₃, and Polymer—Si(ONH₄)₃ before additionto the process stream. It is a convenient feature of this invention thatany of these forms may be added to the process stream. The molecularweight of the polymer should be at least about 500, most preferably atleast about 1000.

In a preferred embodiment, the group containing —Si(OR″)₃, where R″═H,C1-C3 alkyl, aryl, Na, K or NH₄ comprises a group according to—G—R—X—R′—Si(OR″)₃ where G=no group, NH, NR″ or O; R=no group, C═O, O,C1-C10 alkyl, or aryl; X=no group, NR, O, NH, amide, urethane, or urea;R′=no group, O, C1-C10 alkyl, or aryl; and R″═H, C1-C3 alkyl, aryl, Na,K or NH₄.

In one embodiment, the group is —NH—R—X—R′—Si(OR″)₃, where R=no group,O, C1-C10 alkyl, or aryl; X═O, NH, an amide, urethane, or urea; R′=nogroup, O, C1-C10 alkyl, or aryl; and R″═H, C1-C3 alkyl, aryl, Na, K orNH₄.

In another embodiment the polymer to which the group is pendant cancomprise at least one nitrogen to which the pendant group is attached.Exemplary polymers comprising at least one nitrogen to which the pendantgroup is attached include, but are not limited to, a polymer accordingto the following formula:

where x=0.1-100%, y=99.9-0%; and R=no group, C1-C10 alkyl, aryl, or-COX—R′—, where X═O or NH and R′=no group, C1-C10 alkyl or aryl; andR″═H, C1-C3 alkyl, aryl, Na, K or NH₄; wherein polymers according to theformula:

where x=0.5-20%, y=99.5-80% and R=C2-C6 are preferred, and whereinpolymers according to the formula:

where x=0.5-20%, y=99.5-80% are specific examples.

In another embodiment the polymer having pendant thereto a group or endgroup containing —Si(OR″)₃ is derived from an unsaturated polymerizablemonomer containing the group —Si(OR″)₃ where R″═H, C1-C10 alkyl, aryl,Na, K or NH₄ and is optionally copolymerized with one or more additionalpolymerizable monomer(s). Examples of such additional polymerizablemonomers include but are not limited to vinylpyrrolidone,(meth)acrylamide, N-substituted acrylamides such as N-alkylacrylamidesor acrylamidomethylpropanesulfonic acid, (meth)acrylic acid and salts oresters thereof, maleimides, vinyl acetate, acrylonitrile, and styrene.Particularly preferred unsaturated polymerizable monomers containing

—Si(OR″)₃ groups are monomers of formula V and VI.

where

-   -   P═H, C1-C3 alkyl, —CO2R″, —CONHR    -   R═C1-C10 alkyl, aryl,    -   R′═H, C1-3 alkyl, or aryl    -   X═O, NH, or NR    -   R″═H, C1-C3 alkyl, aryl, Na, K or NH₄.        Examples of such polymers include homo- and copolymers of        trialkoxyvinylsilanes such as CH₂═CHSi(OCH₂CH₃)₃ and monomers of        the formula VII:

where P═H, R=—CH₂CH₂CH₂—, R′═H , X=NH and R″═H, C1-C3 alkyl, aryl, Na, Kor NH₄.

Monomers of this type may be copolymerized with any other polymerizablemonomers such as those described above. Particularly preferredcopolymerizable monomers include vinylpyrrolidone, (meth)acrylamide,N-substituted (meth)acrylamides, (meth)acrylic acid and it's salts oresters and maleimides. Particularly preferred are N-substitutedacrylamides containing 4-20 carbon atoms such as N-methylacrylamide,N,N-dimethylacrylamide, N-ethylacrylamide N-propylacrylamide,N-butylacrylamide, N-amylacrylamide, N-hexylacrylamide,N-penylacrylamide, N-octylacrylamide.

In a preferred embodiment a polymer according to the formula:

where w=0-99% , x=1-99%, y=1-99%, z=0.5-20% and M=H, Na, K, NH₄; andR″═H, C1-10 alkyl, aryl, Na, K or NH₄; P═H or CH₃, L═H, or C1-C10 alkyl,aryl or aralkyl,F=—G—R—X—R′—Si(OR″)₃ wherein G=no group, NH, NR″ or O;R=no group, C═O, O, C1-C10 alkyl, or aryl; X=no group, NR, O, NH, amide,urethane, or urea; R′=no group, O, C1-C10 alkyl, or aryl; and R″═H,C1-C3 alkyl, aryl, Na, K or NH₄ and VPD is a moeity derived fromsubstituted or unsubstituted vinylpyrrolidone monomer. Exemplarypolymers are homo- or copolymers of one or more comonomers of formulaeVII:

where P═H, R=—CH₂CH₂CH₂—, R′═H, X═NH and R″═H, C1-C3 alkyl, aryl, Na, Kor NH₄ wherein polymers according to the following formula:

wherein w=0-90%, x=0-50%, Y=0-90%, Z=2-50 mole % are specific examples.

In another embodiment, a polymer according to the formula:

where w=1-99.9%, x=0.1-50%, y=0-50%, z=0-50%; and Q=C1-C10 alkyl, aryl,amide, acrylate, ether, COXR where X=O or NH and R═H, Na, K, NH₄, C1-C10alkyl or aryl, or any other substituent; X═NH, NP where P=C1-C3 alkyl oraryl, or O; R′=C1-10 alkyl, or aryl; V″═H, C1-C3 alkyl, aryl, Na, K orNH₄ or forms an anhydride ring; R″═H, C1-C3 alkyl, aryl, Na, K or NH₄;and D=NR1₂ or OR1 wherein R1═H, C1-C20 alkyl, C1-C20 alkenyl or aryl,with the proviso that all R, R″, V″ and R1 groups do not have to be thesame, is used, and wherein polymers according to the formulae:

where w=1-99.9%, x=0.1-50%, y=0-50%, z=0-50%; and Q is phenyl, and:

where w=1-99.9%, x=0.1-50%, y1+Y2=0-50%, y1 and y2=0-50% z=0-50%; and Qis phenyl are specific examples.

In another embodiment a polymer according to the formula:A—O—(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)(CH₂CH₂O)_(z)—O—B

where x=5-100% (as mole %), y and z=0-100% and at least one A and/or Bunit is a group containing the group —Si(OR″)₃, where R″═H, C1-C3 alkyl,aryl, Na, K or NH₄, is used. Exemplary such polymers include;

-   A—O—(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)(CH₂CH₂O)_(z)—O—B in which A    and/or B═R—Si (OR″)₃, and x=5-50%, y=5-95% and z=0-50% i.e. a    copolymer of ethylene oxide and propylene oxide substituted with    —Si(OR″)₃ groups, and-   A—O—(CH₂CH₂O)_(x)(CH₂CH(CH₃)O)_(y)(CH₂CH₂O)_(z)—O—B in which A    and/or B═x=100%, y=0% and z=0% i.e., a homopolymer of polyethylene    oxide substituted with R—Si(OR″)₃ groups is used.

In another embodiment a polymer prepared from a polysaccharide orpolysaccharide derivative is used. Any polysaccharide to which thependant —Si(OR″)₃ groups can be attached may be employed. Preferably thepolysaccharide should be soluble in the industrial process stream suchas a kraft pulping mill process streams liquor. Polysaccharides usefulin this invention include but are not limited to cellulose and it'sderivatives, such as hydroxyethylcellulose, hydroxypropylcellulose,methylcellulose, hydroxybutylcellulose, carboxymethylcellulose, starchand starch derivatives such as cationic starch, guar, dextran, dextrins,xanthan, agar, carrageenan and the like. Particularly preferred arestarch and cellulose derivatives wherein the reaction product ofhydroxyethylcellulose with 3-glycidoxypropyltrimethoxysilane is aspecific example.

The polymers used in the invention can be made in a variety of ways. Forexample, they can be made by polymerizing a monomer containing the group—Si(OR″)₃, where R″═H, C1-C3 alkyl, aryl, Na, K or NH₄, such as forexample a silane monomer, or copolymerizing such a monomer with one ormore co-monomers. Suitable silane monomers for use in the presentinvention include, but are not limited to vinyltriethoxysilane,vinyltrimethoxysilane, allyltriethoxysilane, butenyltriethoxysilane,gamma-N-acrylamidopropyltriethoxysilane, p-triethoxysilylstyrene,2-(methyltrimethoxysilyl) acrylic acid, 2-(methyltrimethoxysilyl)-1,4butadiene, N-triethoxysilylpropyl-maleimide and other reaction productsof maleic anhydride and other unsaturated anhydrides with aminocompounds containing the —Si(OR″)₃ group. These monomers can behydrolyzed by aqueous base, either before or after polymerization.Suitable co-monomers for use in the present invention include, but arenot limited to, vinyl acetate, acrylonitrile, styrene, (meth)acrylicacid and its esters or salts, (meth)acrylamide and substitutedacrylamides such as acrylamidomethylpropanesulfonic acid,N-methylacrylamide, N,N-dimethylacrylamide, N-ethylacrylamideN-propylacrylamide, N-butylacrylamide, N-amylacrylamide,N-hexylacrylamide, N-phenylacrylamide, N-octylacrylamide. The copolymerscan also be graft copolymers such as polyacrylicacid-g-poly(vinyltriethoxysilane) and poly(vinyl acetate-co-crotonicacid)-g-poly(vinyltriethoxysilane). These polymers can be made in avariety of solvents. Solvents suitable for such use include, but are notlimited to, acetone, tetrahydrofuran, toluene, xylene, etc. In somecases the polymer is soluble in the reaction solvent and is recovered bystripping off the solvent. Alternatively, if the polymer is not solublein the reaction solvent, the product is recovered by filtration.Suitable initiators for use in the present invention include, but arenot limited to, 2,2′azobis(2,4-dimethylvaleronitrile) and2,2-azobisisobutyronitrile, benzoyl peroxide, and cumene hydroperoxide.

In another embodiment of the present invention, polymers useful in theinvention can be made by reacting a compound containing a —Si(OR″)₃group as well as a reactive group that reacts with either a pendantgroup or backbone atom of an existing polymer. For example, polyaminesand polysaccharides can be reacted with a variety of compoundscontaining —Si(OR″)₃ groups to give polymers which can be used for theinvention. Suitable reactive groups include, but are not limited to analkyl halide group, such as for example, chloropropyl, bromoethyl,chloromethyl, and bromoundecyl. The compound containing —Si(OR″)₃, cancontain an epoxy functionality such as glycidoxypropyl, 1,2-epoxyamyl,1,2-epoxydecyl or 3,4-epoxycyclohexylethyl.3-glycidoxypropyltrimethoxysilane is a particularly preferred compound.

The reactive group can also be a combination of a hydroxyl group and ahalide, such as 3-chloro-2-hydroxypropyl. The reactive moiety can alsocontain an isocyanate group, such as isocyanatopropyl, orisocyanatomethyl that react to form a urea linkage. In addition, silanescontaining anhydride groups, such as triethoxysilylpropylsuccinicanhydride are suitable for use in making the polymers for the presentinvention. The reactions can be carried out either neat or in a suitablesolvent. In addition, other functional groups such as alkyl groups canbe added by reacting other amino groups or nitrogen atoms on the polymerwith alkyl halides, epoxides or isocyanates. The polyamines can be madeby a variety of methods. They can be made by a ring openingpolymerization of aziridine or similar compounds. They also can be madeby condensation reactions of amines such as ammonia, methylamine,dimethylamine, ethylenediamine etc. with reactive compounds such as1,2-dichloroethane, epichlorohydrin, epibromohydrin and similarcompounds.

Polymers containing anhydride groups can be reacted with a variety ofcompounds containing —Si(OR″)₃ to make polymers suitable for use in thepresent invention. Suitable anhydride containing polymers includecopolymers of maleic anhydride with ethylenically unsaturated monomerssuch as styrene, ethylene, alpha olefins such as octadecene,meth(acrylamide), (meth)acrylic acid, acrylate esters such as methyl(meth)acrylate, ethyl (meth)acrylate, butyl acrylate andmethylvinylether. The polymer can also be a graft copolymer such aspoly(1,4-butadiene)-g-maleic anhydride or polyethylene-g-maleicanhydride and the like. Other suitable anhydride monomers include, butare not limited to, itaconic and citraconic anhydrides. Suitablereactive silane compounds include, but are not limited toγ-aminopropyltriethoxysilane, bis(gamma-triethoxysilylpropyl)amine,N-phenyl-gamma aminopropyltriethoxysilane, p-aminophenyltriethoxysilane,3-(m-aminophenoxypropyl)-trimethoxysilane, andgamma-aminobutyltriethoxylsilane. Other functional groups can be addedto the polymer by reacting it with amines, alcohols and other compounds.In a preferred polymer for use in the present invention, maleicanhydride is the anhydride and the co-monomer is styrene. A preferredsilane is gamma-aminopropyltriethoxysilane. It is also advantageous toreact some of the anhydride groups with another amine such asdiethylamine.

The same type of amino compound containing an —Si(OR″)₃ group can bereacted with polymers containing a pendant isocyanate group, such ascopolymers of for example, isopropenyldimethylbenzylisocyanate and vinylisocyanate, with co-monomers including, but not limited to, vinylacetate, styrene, acrylic acid, and acrylamide. These polymers can alsobe reacted with other compounds such as amines to enhance performance.

Isocyanate functional compounds with an —Si(OR″)₃ group such asgamma-isocyanatopropyltrimethoxysilane can also be reacted with polymerscontaining hydroxyl groups such as hydrolyzed poly(vinyl acetate) andcopolymers of vinyl acetate with other monomers. Other hydroxylcontaining polymers suitable for use include, but are not limited to,polysaccharides and polymers containing N-methylolacrylamide.

In the present process, the amount of polymer added to the processstream can depend on the composition of the industrial process stream(e.g. a Kraft pulping mill process streams liquor involved and generallyall that is required is an aluminosilicate containing scale inhibitingamount thereof. In general the polymer is preferably added to theprocess stream in economically and practically favorable concentrations.A preferred concentration is one that is greater than about 0 ppm toabout 300 ppm, more preferably in a concentration that is greater thanabout 0 ppm to about 50 ppm and most preferably the polymer is added tothe process stream in a concentration that is greater than about 0 ppmto about 10 ppm.

The polymer can be added directly to any industrial process stream wherescaling can occur, e.g. in the black liquor evaporators of the kraftpulp milling process, and in green and white liquor process streams ofthat process. It is preferred, however to add the polymer to a chargestream or recycle stream or liquor leading to the black liquorevaporator. While the polymer can be added to the industrial processstream at any time during the process, it is preferable to add it at anyconvenient point in the process before or during application of heat.Usually, the polymer is added immediately before the evaporator.

EXAMPLES Preparation of Polymers Example 1 Polymer 1

10.0 gm of a 1.1:1 styrene/maleic anhydride (MA) copolymer is stirred in100 ml of toluene under nitrogen. A mixture of 1.72 gm of butylamine(0.50 mole on MA) and 1.66 gm of aminopropyltriethoxylsilane (0.16 moleon MA) in 10 ml of toluene is added, and the mixture is refluxed undernitrogen for 3 hours. The mixture is then cooled and filtered. The solidpolymer is washed twice with hexane and dried at 60° C. Aqueous NaOH isthen added to the polymer prior to use in order to hydrolyze andneutralize the ethoxysilyl groups. The product is used as an aqueoussolution of the sodium salt.

Example 2 Polymer 2

A 1.1:1 styrene/maleic anhydride (MA) copolymer (molecular weight16,000) is reacted as a dispersion in toluene with tallowamine (0.16mole ratio on MA), triethoxysilylpropylamine (0.16 mole ratio on MA),and diethylamine (0.68 mole ratio on MA). Aqueous NaOH is then added tothe dispersion in order to hydrolyze and neutralize the ethoxysilylgroups. The product is isolated and used as an aqueous solution of thesodium salt. The composition is shown by NMR to be:

Example 3 Polymer 3

Preparation of the tetrapolymer of N-tert-octylacrylamide, acrylic acid,1-vinyl-2-pyrrolidone, and TESPA (triethoxysilylpropylacrylamide) togive a polymer containing 5 mole % silane containing monomer units is asfollows: 1.89 g of 1-Vinyl-2-pyrrolidone, 0.66 g acrylic acid, 2.21 gN-tert-octylacrylamide, 1.30 g TESPA (triethoxysilylpropylacrylamide),(42% in THF), and 0.14 g 2-mercaptoethanol are dissolved in 14 g DMF and11.64 g dioxane and purged with nitrogen. The mixture is heated to 75°C. and 0.16 g 2,2′-azobis(2,4-dimethylvaleronitrile) in 3 g dioxane isadded. After 6 hr at 75° C., the mixture is cooled, giving the desiredpolymer in solution. The polymer is further purified by precipitationwith isopropyl alcohol, washed, and dried. This gives a polymercontaining 42.5 mole % 1-vinyl-2-pyrrolidinone, 22.5 mole % acrylicacid, 5 mole % TESPA, and 30 mole % N-tert-octylacrylamide.

Example 4 Polymer 4

Preparation of the copolymer of 1-vinyl-2-pyrrolidone and TESPA(triethoxysilylpropylacrylamide) to give a polymer containing 5 mole %silane containing monomer units is as follows: 4.69 g of1-Vinyl-2-pyrrolidone, 1.44 g TESPA (42% in THF), and 0.14 g2-mercaptoethanol are dissolved in 12.5 g DMF and 13.07 g dioxane andpurged with nitrogen. The mixture is heated to 75° C. and 0.16 g2,2′-azobis(2,4-dimethylvaleronitrile) in 3 g dioxane is added. After 6hr at 75° C., the mixture is cooled, giving the desired polymer insolution with 15% concentration. This gives a polymer containing 95 mole% 1-vinyl-2-pyrrolidinone and 5 mole % TESPA.

Example 5 Polymer 5

Preparation of the reaction product of polyethylene oxide with3-glycidoxypropyltrimethoxysilane to give a polymer containing 2.2 mole% silane containing monomer units is as follows: 20.0 g ofpolyethyleneoxide (M_(n) about 2000) is dissolved in 10.0 g DMSO andpurged with nitrogen. To this mixture is added 2.63 g3-glycidoxypropyltrimethoxysilane, followed by 1.36 g of 45% KOH. Theresulting mixture is heated to 80° C. for 1 hr, giving the desiredpolymer in solution with 65.8% concentration. This gives a polymercontaining about 97.8 mole % ethylene oxide and 2.2 mole %3-glycidoxypropyltrimethoxysilane.

Example 6 Polymer 6

Preparation of the reaction product of poly(ethyleneglycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) with3-glycidoxypropyltrimethoxysilane to give a polymer containing 3.1 mole% silane containing monomer units is as follows: 30.0 g of poly(ethyleneglycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (with50 wt % ethylene oxide and M_(n) about 1900) is mixed with 4.52 g3-glycidoxypropyltrimethoxysilane under nitrogen. 2.34 g 45% KOH isadded and the resulting mixture heated to 80° C. for 1 hr, giving thedesired polymer with 92.6% concentration. This gives a polymercontaining about 55.1 mole % ethylene oxide, 41.8 mole % propyleneoxide, and 3.1 mole % 3-glycidoxypropyltrimethoxysilane.

Example 7 Polymer 7

Preparation of the reaction product of polyethylenimine with3-glycidoxypropyltrimethoxysilane is as follows. 81.4 g Polyethylenimine(Lupasol WF (BASF); M_(w) about 25,000) is mixed with 18.6 g3-glycidoxypropyltrimethoxysilane, and the resulting mixture is heatedat 60° C. for 16 hr, giving the desired polymer as a soft friable gel.The resultant polymer contained 4.0 mole % silane monomer units. Foruse, the above polymer is dissolved in an aqueous solution of 20 g/lNaOH in order to hydrolyze the trimethoxysilane groups to the sodiumsalt form.

Example 8 Polymer 8

Preparation of the reaction product of hydroxyethyl cellulose with3-glycidoxypropyltrimethoxysilane. 8.0 g dry hydroxyethyl cellulose(molecular weight 24,000-27,000) is mixed with 2.0 g3-glycidoxypropyltrimethoxysilane in 5 g acetone. The acetone is removedby evaporation and the resulting mixture heated at 100° C. for 16 hr,giving the desired polymer containing 15 mole % silane-containingmonomer units. For use, the above polymer is dissolved in an aqueoussolution of 100 g/l NaOH.

Kraft Pulp Mill Scale Inhibition Testing.

In order to simulate the conditions found in a typical kraft pulp millblack liquor a synthetic process liquor simulating a typical blackliquor is prepared in the following way.

A basic aluminate solution is prepared according to the recipe below byadding the aluminate and NaOH solution to the water and stirringovernight. The solution is then filtered through a 3-μm filter membrane(Pall Versapor-3000 T w/wa, 47 mm):

Na₂O•Al₂O₃•3H₂O 100.0 g 50% NaOH 146.6 g Deionized water 753.4 g Total1000.0 g

This basic aluminate solution is used to prepare a simulated kraft blackliquor solution according to the recipe and procedure below. Sodiumacetate is added to achieve the desired sodium ion concentration.Amounts are in grams and percentages are w/w unless otherwise indicated.

Sodium carbonate 121.9 Sodium sulfate 32.7 Sodium thiosulfate 36.4Sodium hydrosulfide, 60% 70.9 Sodium acetate 445.3 50% sodium hydroxide290.7 29.55% SiO₂ 14.0 Basic aluminate solution 25.1 Deionized water1746 Total 2783 g = 2.30 literCalculated concentration:

-   [CO₃ ²⁻]=0.5 M-   [SO₄ ²⁻]=0.1 M-   [SO₂O₃ ²⁻]=0.1 M-   [SH⁻]=0.33 M-   [Na⁺]=5.7 M-   [OH⁻]=1.6 M-   [Si]=0.03 M-   [Al]=0.01 M

The solution is prepared by adding the sodium carbonate, sodium sulfate,sodium thiosulfate, sodium hydrosulfide, and sodium acetate to the waterwith rapid stirring. After 30 min stirring, the solution is filteredthrough a coarse glass frit to remove minor amounts of insolublematerial. The sodium hydroxide solution, silica solution, and finallybasic aluminate solution is added, with stirring after each addition.The solution is used immediately as described below.

Polymer solutions are pre-diluted to 1% (w/w) active concentration in 2%NaOH solution prior to use.

The amount of 1.45 g of a polymer solution, (or 1.45 g of water for thecontrol test), is added to a labeled 4-oz HDPE wide-mouth jar. Then 145g (120 ml) of simulated kraft black liquor solution is added to each jarbefore capping and shaking. Each jar then contained a “test solution”.The polymer dose is 100 ppm.

The caps on the jars are then loosened so as to be able to relievepressure, and the jars placed on the floor of a 102° C. oven to simulateheating in a kraft process liquor. After 1.5 hr the caps are tightenedand the jars placed on a rotisserie placed inside the oven. Afterturning on the rotisserie in the oven overnight (16.5 hr), each sampleis filtered using a pre-weighed 3-μm filter membrane (Pall Versapor-3000T w/wa, 47 mm). Each membrane plus any collected solid is washed withabout 5-ml water and placed on a 2.5-inch diameter watch glass. A steeltray containing all the watch glasses and membranes is placed in a 102°C. oven for 30 min to dry the filtered solids. Each membrane plus solidis weighed and the weight of the solid calculated by difference. % Scaleinhibition is then calculated in the following manner:

% Scale inhibition=

${\%\mspace{14mu}{Scale}\mspace{14mu}{inhibition}} = {100 \times \frac{{Weight}\mspace{14mu}{of}\mspace{14mu}{scale}\mspace{14mu}{formed}\mspace{14mu}{with}\mspace{14mu}{polymer}\mspace{14mu}{present}}{{Weight}\mspace{14mu}{of}\mspace{14mu}{scale}\mspace{14mu}{formed}\mspace{14mu}{with}\mspace{14mu}{polymer}\mspace{14mu}{absent}}}$

The results of testing polymers of examples 1-8 at 100 ppm are shown inTable 1.

TABLE 1 Example Polymer % scale reduction* 9 1 10.3 10 2 27.5 11 3 98.012 4 65.1 13 5 96.1 14 6 96.5 15 7 6.2 16 8 28.7 *Calculated relative tomean of blank runs using mean of two runs.

1. A method for reducing the formation of aluminosilicate containingscale on equipment used in an industrial process having an alkalineprocess stream in which aluminosilicate scaling occurs, comprising thestep of: adding to the alkaline process stream an aluminosilicatecontaining scale inhibiting amount of a polymer having at least 0.5 mole% of a group of the formula I:—Si (OR″)₃  Formula I where R″=H, C1—C10 alkyl, aryl, Na, K or NH₄ as anend group or pendant thereto.
 2. The method according to claim 1,wherein the industrial process is a kraft pulping mill process.
 3. Themethod according to claim 2, wherein the group comprises a groupaccording to formula II:—G—R—X—R′—Si (OR″)₃  Formula II where G=no group, NH, NR″or O; R=nogroup, C═O, O, C1-C10 alkyl, or aryl; X=no group, NR, O, NH, arnide,urethane, or urea; R′=no group, O, C1-C10 alkyl, or aryl; and R″=H,C1-C3 alkyl, aryl, Na, K or NH₄.
 4. The method according to claim 2,wherein the polymer comprises at least one nitrogen to which the groupis pendant thereto.
 5. The method according to claim 4, wherein thepolymer comprises a polymer according to formula III:

where x=0.1-100%, y=99.9-0%; and R=no group, C1-C10 alkyl, aryl, or—COX—R′—, where X=O or NH and R′=no group, C1-C10 alkyl or aryl; andR″=H, C1-C3 alkyl, aryl, Na, K or NH₄.
 6. The method according to claim5, wherein R =C2—C6 alkyl.
 7. The method according to claim 6, whereinthe polymer is a polymer according to the formula IV:

where x=0.5-20%, y=99.5-80%.
 8. The method according to claim 1 in whichthe polymer is derived from an unsaturated polymerizable monomercontaining the group —Si(OR″)₃ where R″=H, C1-C10 alkyl, aryl, Na, K orNH₄ and is optionally copolymerized with one or more polymerizablemonomer(s).
 9. The method according to claim 8, in which the polymer isa homopolymer or copolymer derived from an unsaturated monomer offormula V or VI:

where P=H, C1-C3 alkyl, —CO2R″, —CONHR R=C1-C10 alkyl, aryl, R′=H, C1-C3alkyl, or aryl X=O, NH, or NR R″=H, C1-C3 alkyl, aryl, Na, K or NH₄. 10.The method according to claim 9, in which the polymer is derived frommonomers of formulae V or VI and one Or more polynierizable monomersselected from the group, vinylpyrrolidone, (meth)acrylamide,N-substituted acrylamides, (xneth)acrylic acid and salts thereof oresters and maleimide.
 11. The method according to claim 10, in which thepolymer is a copolymer of one or more comonomers of formulae V or VI andone or more comonomers selected from the group consisting ofvinylpyrrolidone, acrylamide, N-substituted acrylamides containing from4-20 carbon atoms, (meth)acrylic acid and salts thereof.
 12. The methodaccording to claim 11, in which the polymer is a copolymer one or morecomonomers of formulae V or VI and one or more comonomers selected fromthe group consisting of vinylpyrrolidone, N-octylacrylamide, acrylicacid and salts thereof.
 13. The method according to claim 12, in whichthe polymer is a homo- or copolymers of one or more comonomers offormulae VII:

where P=H R=—CH₂CH₂ CH₂— R′=H, X=NH R″=H, C1-C3 alkyl, aryl, Na, K orNH₄.
 14. The method according to claim 1, wherein the polymer is apolymer according to formula VIII:

where w=1-99.9%, x=0.1-50%, y=0-50%, z=0-50%; and Q=C1-C10 alkyl, aryl,amide, acrylate, ether, COXR where X═O or NH and R=H, Na, K, NH4, C1-C10alkyl or aryl; X=NH, NP where P=C1-C3 alkyl or aryl, or O; R′C1-C10alkyl, or aryl; V′=H, C1-C3 alkyl, aryl, Na, K or NH₄ or forms ananhydride ring ; R″=H, C1-C3 alkyl, aryl, Na, K or NH₄; and D=NR1₂ orOR1 wherein R1=H, C1-C20 alkyl, C1-C20 alkenyl or aryl, with the provisothat all R, R″, V″ and R1 groups do not have to be the same.
 15. Themethod according to claim 14, wherein the polymer is a polymer accordingto the formula XI:

where w=1-99.9%, x=0.1-50%, y=0-50%, z=0-50%; and Q is phenyl.
 16. Themethod according to claim 14, wherein the polymer is a polymer accordingto the formula X:

where w=1-99.9%, x=0.1-50%, y1+Y2=0-50%, y1 and y2=0-50%; z=0-50%; and Qis phenyl.
 17. The method according to claim 1, wherein the polymer is apolymer according to the formula XI:A—O—(CH₂CH₂O)_(X)(CH₂CH(CH₃)O)_(y)(CH₂CH₂O)_(z) —O—B  Formula XI wherex=5-100%, y and z=0-106% and at least one A and/or B unit is a groupcontaining the group —Si(OR″)₃, where R″=H, C1-C3 alkyl, aryl, Na, K orNH₄.
 18. The method according to claim 17, wherein x=100%, y and z=0%.19. The method according to claim 17, wherein x=5-50%, y=5-95% andz=0-50%.
 20. The method according to claim 1, wherein the polymer is apolysaccharide having pendant thereto a group or an end group containingformula XI:—Si(OR″)₃  Formula XI where R″=H, C1-C10 alkyl, aryl, Na, K or NH₄. 21.The method according to claim 20, in which the polysaccharide is acellulose derivative.
 22. The method according to claim 21, in which thepolysaccharide is hydroxyethylcellulose derivative.
 23. The methodaccording to claim 22, in which the polysaccharide is ahydroxyethylcellulose derivative and is reacted with3-glycidoxypropyltrimethoxysilane.